New Delhi, Jan 6: About 300 'black cat' commandos of the elite counter-terror force, NSG, deployed an assortment of most sophisticated assault weapons and "buster" ammunition tools to neutralise the terrorists who had sneaked into the Air Force base in the border town of Pathankot.

In one of the longest running counter-terror operations in the country, the National Security Guard (NSG) suffered minor and major injuries to its 21 personnel, besides the death of its bomb squad Commanding Officer Lt Col E K Niranjan, since the first detachment of about 160 commandos flew out from the Palam military airbase on January 1 on an IAF transport aircraft.

Sources privy to the operation said two more similar special strike units, with a strength of about 80 'black cats' each, were airlifted to Pathankot from Delhi on January 2 and 3.

They joined their 'buddies' thick in operations at the sprawling airbase, house to the fighter Squadrons of the IAF. They said it was a "New Year call" to the 24x7 'on alert' counter-terrorist unit based at its garrison in Manesar sometime in the afternoon on January 1 and the commandos of the Special Action Group (SAG) were airborne by 1500 hours.

The call to air-dash to Pathankot was made by the Union Home Ministry to the NSG headquarters, which quickly asked its Force Commander in Manesar to prepare the commando team for assault.

The first team were led by NSG Inspector General (Operations) Major General Dushyant Singh even as Director General R C Tayal camped in Pathankot from Sunday.

The sources said the NSG commandos made extensive use of their special weapons like MP-5 assault rifles, Glock pistols, corner-shot guns and a heavy cache of door and wall-busting explosive charges to corner and eliminate the holed-up terrorists.

They said the 'buster' tools, as they are called, were also used during the 2008 Mumbai terror attacks when NSG used them to blow off locked rooms and passages of five-star hotels but some of them used this time were the enhanced variants which the force has procured post the Mumbai operation.

Two terrorists, the sources said, were killed by the NSG men when they were hiding and launching continuous fire and lobbing grenades from a room where the family quarters of the Defence Security Corps (DSC) is located in the airbase. The room was later demolished by the use of heavy fire.

They said the NSG commandos and other security forces, for the last few hours, have been undertaking the "render safe" procedure which entails sanitising the area from hidden improvised explosive devices (IEDs) and booby traps, and hence the operation is taking time.

"Such thing is done after every operation. The area of the IAF base is large and complex hence it is taking time," one of the sources said.

Half-a-dozen sniffer dogs from the canine (K 9) squad along with their handlers have also been pressed into service by the NSG.

While the elite counter-terror and counter-hijack force has not given a name to the operation till now like 'Op Black Tornado' for the 26/11 Mumbai task, the force for the first time lost an officer from its bomb disposal squad.

Thirty-four-year-old Lt Col and Group Captain Niranjan was heading the unit, they said, and was trying to clear and sanitise the body of a terrorist and the surrounding area when a cleverly concealed grenade blew up fatally injuring the officer and five others.

The highly decorated officer was immediately taken to hospital where he breathed his last. He is the 19th martyr of the force which was raised in 1984 for special operations and as a federal contingency force for India.

"He was part of the first team that went to Pathankot on Friday as there were inputs that the terrorists are carrying huge explosives. Niranjan and his bomb disposal men were tasked to aid the fighting units.

"He joined NSG in May, 2014 on deputation from the Engineers Regiment of the Army which he joined in 2004. He was a dare-devil officer and had been part of a special training with the FBI in the US in combating IEDs and deadly explosives a few months ago," one of Niranjan's commando course colleague said, while refusing to be identified.

The NSG had called the officer's martyrdom as an act bearing "exemplary courage and utmost devotion to duty".

Seven security personnel and six terrorists have been killed in the attack.